1. Field of the Invention
The invention relates to monitoring apparatuses for monitoring the operation state of an internal combustion engine, and particularly to such monitoring apparatuses for vehicles in which a frictional coupling device is provided on the drive power transmission path from the internal combustion engine to the drive wheels of the vehicle.
2. Description of the Related Art
In recent years, various measures have been taken to reduce the environmental stress due to emissions of motor vehicles. As one of such measures, environment-oriented internal combustion engines have been developed which reduce the emissions by optimizing the throttle opening degree, the ignition timing, the fuel injection timing, the fuel injection amount, the operation timing of intake and exhaust valves, and so on, under various conditions.
Such optimization control by environment-oriented internal combustion engines uses a particular control logic when the internal combustion engine has been started at a lower temperature. Because an internal combustion engine runs by combusting fuel, the temperature of the internal combustion engine becomes high as it continues to run. Therefore, typically, internal combustion engines are designed such that an optimum combustion state is accomplished at a certain high temperature. Meanwhile, in the case where the internal combustion engine has been started after it was stopped for a long period of time, the temperature of the internal combustion engine remains low for a while after the engine start, and in such a state, a desired combustion state may not be accomplished. To cope with this, the aforementioned cold-engine control logic is used to optimize fuel combustion in a cold condition immediately after the engine start.
The exhaust substances that are emitted from an internal combustion engine in a cold condition immediately after the engine start are called “cold-start emissions”, and the engine control for reducing such cold-start emissions is called “CSS (Cold Start Strategy) control”.
Some of the motor vehicles incorporating an internal combustion engine enabling such CSS control are provided with a monitoring apparatus for monitoring the state of the CSS control, and such a monitoring apparatus is called “CSS monitor” and used to monitor whether the CSS control is being or has been properly executed. More specifically, the CSS monitor ascertains the presence of an abnormality in the operation state of the internal combustion engine based on, for example, the amount of intake air to the internal combustion engine or based on the state of the ignition timing (advanced or retarded).
In vehicles having a manual transmission provided on the drive power path from the internal combustion engine to the drive wheels, a frictional coupling device (clutch device) is provided to allow and interrupt the transmission of the drive power, and the amount of engagement of the frictional coupling device changes as it is operated by the driver. When the driver operates the clutch device at the time of for example, starting the vehicle from a standstill, it causes a relatively large change in the load on the internal combustion engine and the friction (frictional resistance) of the internal combustion engine increases, causing an external disturbance to the combustion of the internal combustion engine.
In view of such influence of the clutch operation by the driver, for example, Japanese Patent Application Publication No. 2000-205011 (JP-A-2000-205011) describes a control apparatus for an internal combustion engine of a vehicle with a manual transmission. This control apparatus prevents making an erroneous determination on the combustion state by suspending the combustion state determination process when the clutch is determined to have been engaged.
However, this control apparatus simply suspends the combustion state determination process when the clutch is determined to have been engaged, that is, JP-A-2000-205011 does not disclose any structure enabling the combustion state determination process to be continued even if the clutch is being operated.
In general, a CSS monitor ascertains the presence of an abnormality of the internal combustion engine at a low temperature and normally performs the ascertainment process only one time after the engine start. Therefore, a sufficient monitoring performance can not be achieved by simply suspending the ascertainment process when a clutch operation is detected. Note that other related technology is described in Japanese Patent Application Publication No. 10-184421 (JP-A-10-184421).